The Clamped Bed Springs: A Four-Armed Wire Ties Them in Squares

"This invention consists in connecting spiral springs at their bases and tops by means of a four-armed bent-wire clamp, which unites the springs in groups of four, and by which an equal and even adjustment of the surface is had when pressure is brought to bear upon the mattress." The clamp "is placed so as to fill the hollow square formed by the four spiral springs, both at the base and at the top", its arms bent round each spring's coil, so that "no part or portion of the mattress or any of the spirals can be moved independent of the others." He notes that four separate clamps round the springs had been proposed, but that "This does not prevent the springs from being raised up and separated to a certain extent when pressure is brought to bear upon the surface, for the reason that there is no center support in the hollow square".

Stand four equal compression springs in a square on a board. Put a small plate on one spring and load it with a weight; measure how far it sinks. Now bend a four-armed clamp from steel wire and hook its arms over the top coils of all four springs, with a second clamp at the bottom. Load the same spring with the same weight and measure again. Compare with the notebook's share-by-four.

**Alexander C. McMains** of San Francisco filed US 160,274 on 7 January 1875; it is dated 2 March 1875. **Honest limits.** The notebook assumes a tied group shares a load equally, as if joined by a stiff plate; real wire ties bend, so the share is less even. Stiffness and loads are examples. Your ruler readings are the measurement.